Ok, I just spent a few hours debugging a cube that wasn’t bringing back any data. Checking all the relationships, the source data, the marts, etc, etc. And lo and behold, find out that a colleague commented out all the calculations, including the CALCULATE statement which says:
The CALCULATE command controls the aggregation of leaf cells in the cube.
If deleted or modified, the data within the cube will be affected.
This command should only be edited if you intend on manually specifying how the cube will be aggregated.
Remember, you NEED the “CALCULATE” command!
Steve Novoselac's Blog 